Composite member comprising metallic sheet bent to be arcuate in section and rigid synthetic resin coating

ABSTRACT

A length composite member comprising a metallic sheet and a rigid synthetic resin coating is bent to be arcuate in transversal section. The thickness of the metallic sheet of such composite member as bent to be arcuate in transversal section is extremely small as compared with the radius of curvature of the desired arcuate sectional curve. A plurality of small arcuate sectional bent portions in transversal section are formed distributed in the transversal or width direction of the metallic sheet. The centers of the respective curvatures of these plurality of small arcuate sectional bent portions in transversal section are selected to exist on the same side as that of the center of curvature of the composite member bent to be arcuate. The metallic sheet is generally bent in advance to be arcuate in transversal section and both main surfaces of the metallic sheet thus bent are coated with rigid synthetic resin. The thickness of the coated layers of the rigid synthetic resin is selected to be sufficiently large as compared with that of the metallic sheet.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a composite member comprising ametallic sheet and a rigid synthetic resin coating. More specifically,the present invention relates to a length composite member of such as agutter comprising a metallic sheet coated with rigid synthetic resinbent to be arcuate in transversal section or in width directionalsection.

2. Description of the Prior Art

In the case where a member arcuate in transversal section is fabricatedonly with rigid synthetic resin, such arcuate sectional member involvesthe shortcomings of the rigid synthetic resin per se, i.e. theshortcomings of small antishockness and liability of thermaldeformation. Although such shortcomings can be overcome to some extentby selecting a material of rigid synthetic resin and the kind of anadditive, the simplest and straightforward approach to that end is toincrease the thickness of the arcuate sectional member. However, inconsideration of the recent requirement of saving materials and energy,it is desired to provide a member of similar performance by decreasingthe source material rather than simply increasing the thickness of themember. One approach which was thought of is to embed a thin metallicsheet in an arcuate sectional member made of rigid synthetic resin. Morespecifically, such approach fulfills the above described shortcomings ofa thin rigid synthetic resin sheet by the use of a metallic sheet, whileskillful use is made of anticorrosiveness, tinting power, moldabilityand the like which are the features of rigid synthetic resin.

In order to embed a thin metallic sheet in a rigid synthetic resinmaterial, a preferred approach is a method of bending continuously athin metallic sheet with several stages of forming rolls, thereby toform the same to be arcuate in transversal section with a desired curvedsurface and of coating both surfaces thereof with synthetic resin,inasmuch as the same can be carried out with a high production speed ona mass production basis. However, the above described method involves aproblem that in the case where the thickness of a metallic sheet isextremely small as compared with the radius of curvature of the arcuatesectional member thus formed a spring back is encountered in rollforming a metallic sheet to be arcuate in section. More specifically,when a metallic sheet is bent to be arcuate in section by force and theforce is removed, the sheet as deformed tends to return to the originalshape due to elastic strain, thereby to cause a spring back. Therefore,in order to attain an arcuate sectional curve of a desired radius ofcurvature, it is necessary to bend the material in consideration of suchspring back. In the case where the thickness of a metallic sheet isextremely small as compared with the radius of curvature of a desiredarcuate sectional curve, it would be required to bend the metallic sheetso much as to curl the same in a cylindrical shape to lap even more thanone and a half of the round. Therefore, in roll forming a metallic sheetwhich is extremely thin as compared with the radius of curvature of adesired arcuate sectional member to be attained, it is very difficultand becomes problematic to bend such metallic sheet. Furthermore, whensuch metallic sheet thus formed to be arcuate in section is coated witha rigid synthetic resin material means of extrusion molding, whereuponthe same is cooled by means of a cooling means, the arcuate sectionalmember after cooling does not become a desired geometry (radius ofcurvature, width, height and the like) unless the same is cooled inconsideration of a spring back of such metallic sheet, and furthermore,when heat is applied to the arcuate sectional member after cooling andthe rigid synthetic resin becomes soft, the arcuate sectional member isdeformed to stretch due to a spring back of the metallic sheet, with theresult that the above described method still involves a disadvantagethat a stabilized shape can be hardly maintained.

SUMMARY OF THE INVENTION

The present invention comprises a composite member comprising a metallicsheet coated with a rigid synthetic resin material, wherein the metallicsheet is formed to be generally arcuate in transversal section beforethe same is coated with the synthetic resin material, whereupon aplurality of small arcuate sectional bent portions are formed extendingin the longitudinal direction and distributed in the transversaldirection such that the center of curvature of each of the small arcuatesectional bent portions may be positioned on the same side as that ofthe center of curvature of the arcuate sectional curve in transversalsection of the composite member, whereupon the metallic sheet bent to bearcuate in transversal section is coated with the rigid synthetic resinmaterial.

According to the present invention, even in bending or curving ametallic sheet to be arcuate in transversal section prior to the step ofcoating the same with a rigid synthetic resin material, a spring back isdecreased as a function of a plurality of small arcuate sectional bentportions extending in the longitudinal direction and distributed in thetransversal direction or the width direction, which more facilitatesformation of a metallic sheet in curvature to be arcuate in transversalsection. Furthermore, even after the step of coating the rigid syntheticresin material, little spring back is caused in the metallic sheet,which simplifies cooling of the synthetic resin layers and enablesmaintenance of the composite member after cooling in an extremelystabilized form of curvature, i.e. of being arcuate in transversalsection. Formation of a plurality of small arcuate sectional bentportions extending in the longitudinal direction and distributed in thetransversal direction or the width direction enhances the tensilestrength of a metallic sheet in continuously forming such compositemember, with the result that workability and facility of formation aremuch enhanced.

In a preferrred embodiment of the present invention, those in-betweenportions between the two adjacent small arcuate sectional bent portionsextending in the longitudinal direction and distributed in the widthdirection are further curved or bent to be arcuate in transversalsection with a relatively large radius of curvature. The in-betweenarcuate sectional portions between the above described small arcuatesectional bent portions are curved such that the center of curvature ofeach of the in-between arcuate sectional portion exists on the sideopposite to the center of curvature with which the composite member perse is curved. Formation of those in-between arcuate sectional portionsbetween the plurality of small arcuate sectional bent portions in suchcurvature as to be arcuate in transversal section in the directionopposite to the direction of curvature of the composite member per semore facilitates formation of the plurality of small arcuate sectionalbent portions and further decreases a possible spring back in themetallic sheet.

In fabricating such a composite member as described above, a metallicsheet is in advance roll formed prior to the step of coating the samewith a rigid synthetic resin material. Two approaches are available inperforming such roll forming step. One of them comprises the steps ofbending a metallic sheet as a whole to be arcuate in transversal sectionor in width section and thereafter forming a plurality of small arcuatesectional bent portions as described above on the thus bent metallicsheet. The other method comprises the steps of forming a plurality ofsmall arcuate sectional bent portions on a flat metallic sheet and thenbending the metallic sheet having the plurality of small arcuatesectional bent portions formed to be arcuate as a whole in transversalsection. According to the latter mentioned method, the plurality ofsmall arcuate sectional bent portions can be uniformly formed in formingthe small arcuate sectional bent portions. Furthermore, after theplurality of small arcuate sectional bent portions are formed on a flatmetallic sheet, the metallic sheet is naturally curved as a whole to bea desired arcuate sectional curvature. Therefore, the step of rollforming the metallic sheet to curve the same as a whole to be arcuate intransversal section is simplified and accordingly the fabricatingfacilities and the space for fabrication may be small.

Accordingly, a principal object of the present invention is to provide acomposite member comprising a metallic sheet bent with littlepossibility of spring back and a rigid synthetic resin coating coveringthe same.

One aspect of the present invention resides in a composite membercomprising a metallic sheet and a rigid synthetic resin coating thereof,wherein the metallic sheet is formed with a plurality of small arcuatesectional bent portions extending in the longitudinal direction anddistributed in the transversal or width direction of the metallic sheetand is bent to be arcuate in transversal section, with the centers ofthe curvatures of these small arcuate sectional bent portions selectedto exist on the same side as that of the center of the curvature to bearcuate in transversal section of the composite member.

Another aspect of the present invention resides in a composite membercomprising a metallic sheet and a rigid synthetic resin coating thereof,wherein the metallic sheet can be curved or bent with extreme simplicityand stability.

A further aspect of the present invention resides in a composite membercomprising a metallic sheet and a rigid synthetic resin coating thereof,wherein the metallic sheet is curved or bent with stability to bearcuate in transversal section in and after coating the metallic sheetwith a rigid synthetic resin material.

Still a further aspect of the present invention resides in a process formanufacturing a composite member comprising a bent metallic sheet and arigid synthetic resin coating thereof with excellent productivity.

These objects and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a gutter which is an example of acomposite member in accordance with the present invention;

FIG. 2 is a block diagram showing one embodiment of an apparatus formanufacturing a composite member as shown in FIG. 1;

FIG. 3 is a front view showing one example of an upper and lower formingrolls of a roll forming machine;

FIG. 4 is an enlarged partial sectional view showing one example of alower forming roll;

FIG. 5 is a sectional view showing one example a mold for coating ametallic sheet with a rigid synthetic resin material;

FIG. 6 is a sectional view taken along the line VI--VI in FIG. 5;

FIGS. 7A to 7G are sectional views showing the states after formation ofa metallic sheet at the respective steps of the FIG. 2 embodiment;

FIG. 8 is an enlarged partial sectional view of another example of alower forming roll;

FIG. 9 is a block diagram showing another embodiment of an apparatus formanufacturing the FIG. 1 composite member;

FIGS. 10 and 11 are enlarged partial sectional views showing examples ofa lower forming roll for use in the FIG. 9 embodiment; and

FIGS. 12A to 12G are sectional views showing the states after formationof a metallic sheet at the respective steps of the FIG. 9 embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a perspective view of an end portion of one embodiment of acomposite member in accordance with the present invention. Specifically,the composite member 1 comprises a gutter. The composite member 1comprises a metallic sheet 2 of 0.15 mm in thickness, for example, bentto be arcuate in transversal section with the radius of curvature of 50mm, both side edges being inwardly curved to form curled portions 12.Although not shown in FIG. 1, the composite member 1 is further formedwith a plurality of small arcuate sectional bent portions orprotuberances protruding downward as viewed in FIG. 1 and extending inparallel in the longitudinal direction and distributed in thetransversal or width direction. The composite member 1 further comprisesa coating 3 of rigid synthetic resin covering the whole outer surface,i.e. both main surfaces of the metallic sheet 2. The radius of curvatureof each of the small arcuate sectional protuberances is 0.5 mm, forexample, and in the embodiment shown eleven small arcuate sectionalprotuberances are formed extending in parallel in the longitudinaldirection by means of a lower forming roll 54a shown in FIGS. 3 and 4.The width of the metallic sheet 2 before the same is curved is 180 mm,for example.

As shown in FIG. 1, the inventive composite member may employ a metallicsheet and a rigid synthetic resin material conventionally employed. Morespecifically, the metallic sheet 2 may comprise a sheet of metal such asiron, aluminum, copper or the like and in particular, in case of an irona cool rolled steel sheet, a stainless steel sheet and the like may beused. The rigid synthetic resin coating 3 may be of vinyl chlorideresin, acrylic resin, AAS resin, ABS resin or the like, in which anadditive, a filler and the like may be admixed as desired.

The purpose of forming the curled portions 12 is to prevent deformationlike corrugation at both sides of the curved metallic sheet 2 after rollforming and to prevent deformation like corrugation at both sides of agutter which is a final product of an embodiment of the presentinvention. The geometry of the curled portions 12 may be determined tobe optimal depending on a final product of the embodiment.

FIG. 2 is a block diagram showing an apparatus for manufacturing thecomposite member 1 shown in FIG. 1. In order to improve the adhesivenessof a rigid synthetic resin coating to the metallic sheet, an adhesiveagent is coated on both main surfaces of the metallic sheet 2 beforeforming as shown in FIG. 7A and is dried. Thereafter the metallic sheet2 is wound in a coil and is set on an uncoiler 4. The uncoiler 4 is notcoupled to a driver such as a motor, so that the same may be freelyrotated. Accordingly, when the metallic sheet 2 is drawn in the arrowdirection by means of a drawer 9, the uncoiler 4 is rotated to unwindand yield the metallic sheet 2. The metallic sheet 2 fed from theuncoiler 4 is formed to be arcuate in transversal or width section witha desired curvature, as shown in FIG. 7E, by means of a roll formingmachine 5. The roll forming machine 5 comprises five-stage forming rolls51, 52, 53, 54 and 55 arranged to be paired as upper and lower, althoughthe number of stages may be selected to be several stages to severaltens stages as necessary.

In the embodiment shown, the three forming rolls 51, 52 and 53 at theearlier stages are used to form the curled portions 12 in the metallicsheet 2 in succession as shown in FIGS. 7B, 7C and 7D, while the formingrolls 54 and 55 at the latter stages are used to bend the metallic sheet2 as shown in FIG. 7E and to form a plurality of small arcuate sectionalprotuberances 151 shown in FIG. 7F in the curved portion 13 of themetallic sheet 2. The forming rolls 54 and 55 at the latter aresubstantially the same configuration and the forming roll 54 comprises alower forming roll 54a and an upper forming roll 54b, as shown in FIG.3, the lower forming roll 54a being made of metal. As shown in FIG. 4 or8, the lowr forming roll 54a is shaped such that a section taken in theplane in parallel with a rotational shaft 14 (FIG. 3) and including thesaid rotational shaft is arcuate with the radius R of curvature with aplurality of (five in each of FIGS. 4 and 8) small arcuate sectionalportions formed on the said arcuate sectional portion each with a smallradius r of curvature protruding outward from the arcuate sectionalportion. Accordingly, the center O of curvature and the centers P ofcurvature are positioned on the same side with respect to the metallicsheet. FIGS. 4 and 8 show the above described section and accordingly itfollows that the respective small arcuate sectional portions 15 areformed as annular protuberances extending around the rotationalperiphery (arcuate in section) of the lower forming roll 54a.

By way of an example, the radius R of curvature of the large arcuatesectional curve is 50 mm and the radius r of curvature of the smallarcuate sectional portions 15 is 0.5 mm in the embodiment shown.

In the foregoing the sectional configuration of the lower forming roll54a shown in FIG. 4 was described as arcuate in section with the radiusR of curvature for facility of description; however, in actuality thosein-between portions between the adjacent two small arcuate sectionalportions 15 each having the radius r of curvature are not arcuate butrather linear. In the case of the another embodiment of the lowerforming roll 54a shown in FIG. 8, instead those in-between portionsbetween the two adjacent small arcuate sectional portions 15 are formedto be arcuate as at 17 in section of the radius r1 of curvature with thecenters Q of curvature on the side opposite to that of the center O ofcurvature of the above described radius R of curvature with respect tothe large arcuate sectional curve. The radius r1 of curvature of thearcuate sectional curve 17 of the in-between portions may be 2 to 10 mm.The rotational periphral surface of the lower forming roll 54a issuitably plated to improve contact with the metallic sheet 2.

As shown in FIG. 3, the rotational peripheral surface of the upperforming roll 54b is formed with an arcuate sectional concave groove 16corresponding to the arcuate sectional convex curve of the lower formingroll 54a and the surface of the arcuate sectional groove 16 for contactwith the lower forming roll 54a is formed with hard rubber. By hardrubber, it is intended to mean hard urethane rubber, butyl rubber,silicon rubber, natural rubber and the like and the hardness thereof maybe properly selected in consideration of the material, the thickness andthe like of the metallic sheet 2; however, in the embodiment shown hardurethane of the hardness of 70 to 80 is adhered onto the surface of thearcuate sectional groove 16 with the thickness of 5 to 10 mm.

The metallic sheet 2 coming out of the forming rolls 51, 52 and 53 atthe earlier stages has the curled portions 12 formed as shown in FIG. 7Dand is then entered into the forming rolls 54 and 55 at the latterstages, when the curved portion 13 of the metallic sheet is stronglypressed toward the hard rubber portion of the upper forming roll 54b bymeans of the lower forming roll 54a. As a result, the curved portion 13is pressed in part to make inroad into the hard rubber portion by meansof the small arcuate sectional portions 15 of the lower forming roll54a, whereby a plurality of small arcuate sectional protuberances areformed in the curved portion 13.

By using the lower forming roll 54a as shown in FIG. 8, the curvedportion 13 of the metallic sheet 2 can be strongly pressed toward theupper forming roll 54b inasmuch as the in-between arcuate sectionalportions 17 with the radius r1 of curvature and the small arcuatesectional portions 15 with the radius r of curvature are protruded inthe directions opposite to each other, with the result that formation ofthe small arcuate sectional protuberances on the metallic sheet 2 isfacilitated. However, in such a case, the in-between arcuate sectionalcurves between the small arcuate sectional protuberances of the metallicsheet 2 deformed by the arcuate sectional portions 17 with the radius r1of curvature are preferably mitigated with the forming roll 55 at thefollowing step.

Returning again to FIG. 2, the metallic sheet 2 formed to a desiredarcuate sectional curve by means of the roll forming machine 5 is causedto pass through a preheater 6 at the following step. At that time theadhesive agent coated in advance on the metallic sheet 2 and dried ispreheated by the heater of the preheater 6. The temperature of thepreheater 6 is selected to be a value close to a coating temperature ofthe rigid synthetic resin material and the metallic sheet 2 and theadhesive agent on both main surfaces are heated to that temperature. Inthe case where rigid vinyl chloride resin is employed, such temperaturewould be 170° C. to 180° C. In the case where the metallic sheet 2 hasnot been coated with an adhesive agent, a coating apparatus for coatingan adhesive agent on both main surfaces of the metallic sheet 2 isdisposed at the position of the preheater 6. The coating apparatus maybe such an apparatus as a roll coater or the like.

The adhesive agent may be of an acrylic resin group, an epoxy resingroup, a vinyl chloride group, a group of vinyl chloride-vinyl acetatecopolymer or the like.

After the metallic sheet formed to be arcuate in transversal section ispreheated by the preheater 6, the resin material is coated on themetallic sheet by means of a rigid synthetic resin coating mold 7 (FIGS.5 and 6). More specifically, both surfaces of the metallic sheet 2 arecoated with the rigid synthetic resin material 3 extruded from anextruder 71 in the direction normal to the traveling direction of themetallic sheet 2, whereby a composite member 1 is provided. FIG. 5 is atransversl sectional view of the mold 7 and FIG. 6 is a sectional viewtaken along the line VI--VI in the FIG. 5 mold 7. The molten resinextruded from the extruder 71 is fed through the resin path 72 to coatat least both main surfaces of the metallic sheet 2, as shown in FIG.7G, passing through a slit in the mold 7. A molding temperature of therigid synthetic resin is approximately 190° C. to 210° C. and thetemperature of the coated layer of the rigid synthetic resin 3 of thecomposite member 1 immediately after passage through the mold 7 would beapproximately 170° C. to 180° C.

The composite member 1 passing through the mold 7 is then rapidly cooledby means of a cooling means 8. Since it follows that the metallic sheet2 is included in the cooling means 8 as a core material, no sizing moldis required and specifically means for directly passing the compositemember 1 through a water tab or means for passing the same while wateris sprayed is employed, the latter mentioned means being more effectivein rapidly cooling the composite member 1.

After passing through the cooling means 8, the composite member 1 isdrawn by means of a drawer 9. The drawer 9 is driven by a prime moversuch as a motor, while the composite member 1 is sandwiched from upwardand downward by means of a chuck of hard rubber and is fed. Morespecifically, in the case of the manufacturing apparatus of theembodiment, the metallic sheet or the composite member 1 are continuallyfed to travel by means of the drawer 9. The traveling speed is selectedto be 10 to 20 m/min.

Now the composite member 1 is cut to a predetermined length by means ofa cutter 10. The cutter 10 is provided with a detector such as a limitswitch, photodetector, or the like, such that when the composite member1 reaches the position of the detector the same is detected by thedetector to be cut into a predetermined length.

Since the metallic sheet 2 is wound in a coil and is mounted to theuncoiler 4 in continually forming the composite member 1, the wholeapparatus is brought to a stop when the metallic sheet 2 runs out. Inorder to continually achieve the forming operation, therefore, ajointing means, such as a welder, is provided between the uncoiler 4 andthe roll forming machine 5 for jointing the trailing end of the metallicsheet 2 and the leading end of the following metallic sheet 2 wound in acoil and mounted to the uncoiler 4. A press for punching the metallicsheet 2 may be provided at the same position, in which case the rigidsynthetic resin coated on both surfaces of the metallic sheet 2 is madeintegral by fusion through the punched apertures of the metallic sheet,thereby to considerably enhance the coating strength.

In the embodiment shown, the metallic sheet 2 formed to be arcuate intransversal section by means of the roll forming means (the roll formingmachine 5) has an extremely small thickness t as compared with theradius R of curvature of the desired arcuate sectional curve, in whichthe ratio thereof may be expressed by the following formula:

    (t/R)<0.01

Referring to the relation expressed by the foregoing formula, accordingto the conventional approach, even if the metallic sheet 2 is curvedwith the radius R of the curvature, the metallic sheet 2 is liable tostretch due to a spring back of elastic strain when the curving force isremoved, with the result that a desired arcuate sectional curve is notattained; however, according to the present invention, the metallicsheet is formed to be arcuate in transversal section by means of theroll forming means such that a plurality of small arcuate sectional bentportions are formed on the desired arcuate curved plane such that thecenters P of curvature of the small arcuate sectional bent portions maybe positioned on the same side as that of the center O of curvature ofthe desired arcuate sectional curved plane and, therefore, a spring backis little caused and the desired arcuate sectional curvature is attainedwith stability. More specifically, by way of one example, according tothe present invention such advantage is effectively brought about in thecase where the thickness of the metallic sheet 2 is smaller than (1/100)of the radius R of curvature of the desired arcuate sectional member 1.

More specifically, the present invention brings about the advantage thatformation of small arcuate sectional bent portions on a metallic sheetrelatively increases a ratio of the thickness t of the metallic sheet tothe radius R of curvature of an arcuate sectional curve of the metallicsheet even in the case where the thickness t of the metallic sheet 2 isvery small as compared with the radius R of curvature of the arcuatesectional curve of the metallic sheet, with the result that a springback is little caused due to the small arcuate sectional bent portionseven after the force is removed after formation through roll forming andhence the arcuate sectional curve is stable even after the metallicsheet is coated with a rigid synthetic resin material.

Now a specific example of the composite member of a gutter shown will bemore specifically described. The metallic sheet 2 may be of a coolrolled steel sheet (SPCC) of the thickness t of 0.15 mm and the radius Rof curvature of the arcuate sectional curve of the desired arcuatesectional member 1 is 50 mm. In such a case, assuming that the radius rof curvature of the small arcuate sectional bent portions of the lowerforming roll 54a of the forming roll 54 is 0.5 mm and the radius r1 ofcurvature of the in-between arcuate sectional curves between the twoadjacent small arcuate sectional bent portions is 6 mm or the smallarcuate sectional bent portions are formed at the angular intervals of3° to 5°, the metallic sheet 2 can be formed to attain the desiredradius R of curvature being 50 mm through roll forming.

In the case of the above described FIG. 2 embodiment, after the metallicsheet 2 is bent or curved in transversal or width section, as shown inFIGS. 7A to 7G, the same is further formed with the small arcuatesectional bent portions 151 by means of the forming roll 54. However, inthe case where the metallic sheet 2 is formed with the small arcuatesectional portions 151 after bending the same, it was observed throughexperimentation by the inventors that the following problem is involved.More specifically, since the metallic sheet 2 is a very thin steel sheetthe thickness t of which is as small as 0.15 mm, it is difficult to makeuniform the gap between the two rolls 54a and 54b, if such forming roll54 as shown in FIG. 3 is employed. Therefore, a depressing force ontothe upper forming roll 54b becomes non-uniform among a large diameterportion and a small diameter portion of the lower forming roll 54a asshown in FIG. 3, which makes non-uniform the geometry of each of thethus formed small arcuate sectional protuberances 151, which is furtherliable to cause deformation. More specifically, although the metallicsheet 2 as curved as shown in FIG. 7E is pressed relatively strongly atthe central portion thereof by means of the two rolls 54a and 54b, thepressing force is insufficient at the side end portion and is not enoughto fully bend the side end portion. Therefore the geometry of the smallarcuate sectional bent portions becomes non-uniform, although the sameshould be inherently uniform.

Under the circumstances, according to another embodiment of the presentinvention, as shown in FIGS. 12A to 12G, the metallic sheet 2 is firstformed with small arcuate sectional bent portions 151' while the same isin a flat state, whereupon the metallic sheet is curved in transversalor width section.

FIG. 9 is a block diagram showing another embodiment of an apparatus formanufacturing the FIG. 1 composite member. The FIG. 9 embodimentcomprises a forming roll 54', which is different from that of the FIG. 2embodiment. More specifically, the lower forming roll 54a' included inthe forming roll 54' of the FIG. 9 embodiment comprises a flat outercontour line as shown in FIGS. 10 and 11, for example. The upper formingroll 54b' corresponding to such lower forming roll 54a' is also made tobe flat at the peripheral side surface, as a matter of course, althoughthe same is not shown. The metallic sheet 2 is formed with small arcuatesectional protuberances 151' while the same is in a flat state, as shownin FIG. 12E, by the use of the forming roll 54'. At that stage theradius of curvature of the arcuate sectional curve in transversalsection of the composite member is determined in consideration of thematerial of the metallic sheet 2, the radius r1 of curvature (FIG. 11)and the pressing force of the forming roll 54'. By forming the smallarcuate sectional protuberances on the metallic sheet 2 while the sameis in a flat state, the metallic sheet 2 can be thereafter curved to bearcuate in transversal section of a desired curve, as shown in FIG. 12F,without passing the same through any particular forming roll. Therefore,according to the embodiment shown, a forming roll for curving themetallic sheet as shown in FIG. 12F is not necessarily required but themetallic sheet 2 is inserted into the mold 7 through the guide roll 55'of a desired sectional curve before the same is coated with a rigidsynthetic resin material.

The FIG. 9 embodiment in which the small arcuate sectional protuberancesare formed on the metallic sheet 2 while the same is in a flat statebrings about the following advantage as compared with the FIG. 2embodiment. More specifically, since the peripheral side surface of bothof the lower forming roll 54a' and the upper forming roll 54b' of theforming roll 54' are generally flat (disregarding convexes and concavesfor forming the small arcuate sectional protuberances), the pressingforce is uniformly applied throughout the width direction of themetallic sheet and therefore the small arcuate sectional protuberances151' thus formed also become uniform. Furthermore, since the formingroll 54' need not be bent as shown in FIG. 3, manufacture is facilitatedand accordingly a manufacturing cost is decreased. Furthermore, althoughsuch forming roll 54' as shown in FIG. 3 necessitates tiresomemaintenance in order to secure positioning accuracy, the embodiment nowin description of the forming roll 54' having a flat outer peripheralsurface much simplifies such maintenance. In addition, when the metallicsheet 2 is formed with small arcuate sectional protuberances while thesame is in a flat state as shown in FIG. 12E, as described previously,the metallic sheet 2 tends to be naturally bent or curved as shown inFIG. 12F. Therefore, such a forming roll as shown in FIG. 12F forforming the metallic sheet 2 to be arcuate in transversal section may bedispensed with and such forming step is simplified and the manufacturingfacility and space therefore are also decreased. By way of an example,according to the FIG. 2 embodiment, approximately twelve stages offorming rolls are required from the FIG. 7A state to the FIG. 7D stateand in addition three more forming rolls are required to attain the FIG.7E state and two further forming rolls are required to attain the FIG.7F state. By contrast, according to the FIG. 9 embodiment, from the FIG.12A to FIG. 12D corresponding FIGS. 7A to 7D, the same number of stagesare required but thereafter only one stage of forming roll is requiredfor each of FIGS. 12E and 12F.

Now another embodiment of the inventive composite member will bedescribed. Rigid synthetic resin may be the same as that of thepreviously described embodiment. The metallic sheet 2 is of DR-8 of theAISI standard, the hardness being "73" in terms of the Rockwell hardnessH_(R) -30T. The width between the curled portions 12 at both sides ofthe metallic sheet 2 is 140 mm, the thickness t being 0.15 mm. The lowerforming roll 54a' of the forming roll 54' is selected such that theradius r of curvature in FIG. 11 is 0.5 mm and the radius r1 ofcurvature is 5.7 mm. The interval of the small arcuate sectionalprotuberances 151' formed on the metallic sheet 2 was selected to be 2.6mm. The interval between the small arcuate sectional protuberances ischanged depending on the radius r1 of curvature. The angle of the smallarcuate sectional protuberances 151' with respect to the center ofcurvature of the composite member 1 was 3°. The thickness of the wholecomposite member 1 was selected to be 1.0 mm. It is pointed out that theabove described values are merely an example of the inventive compositemember which was employed in experimentation made by the inventors.

Meanwhile, in the foregoing description the arcuate curve in transversalsection of the composite member was considered to be typically as aportion of a circle. However, it is pointed out that for the purpose ofthe present invention a portion of a curve similar to a circle, such asa portion of the periphery of an ellipse, a portion of the periphery ofa parabola, or the like may be employed as the arcuate curve intransversal section of the composite member. Accordingly, the terms"arcuate" and "the center of curvature" used in the disclosure and theappended claims are intended to cover any types of such curvature andthe center of such curvature. For example, even in the case where thearcuate curve in transversal section of the composite member is of acurve the center of curvature of which is not primarily determinable,there could exist a plurality of centers of curvature on the assumptionthat such curvature is divided into a plurality of sections each beingsimilar to a portion of the periphery of a circle having its own centerof curvature, in which case a group of such plurality of centers ofcurvature may be generally considered as a center of curvature in termsof the present invention.

In the foregoing description the plurality of arcuate sectionalprotuberances were described as formed distributed in the transversaldirection and extending continually in the longitudinal direction;however, all of these small arcuate sectional protuberances need notnecessarily extend continually throughout the full length of thecomposite member and instead each of the protuberances may be separateat intervals in the longitudinal direction so that the same may bediscontinuous in the longitudinal direction in a modification of thepresent invention. More specifically, it is intended that the presentinvention covers both an embodiment in which a plurality ofprotuberances are continuous throughout the full length of the compositemember and another embodiment in which the protuberances are separate atintervals in the longitudinal direction to be discontinuous. In the caseof the latter mentioned embodiment, however, it is preferred that theprotuberances are separated at intervals at dislocated positions, withrespect to the adjacent ones, in the longitudinal direction rather thanat the same position in the longitudinal direction.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

What is claimed is:
 1. A composite member bent to be arcuate intransversal section, comprising:a metallic sheet bent to be arcuate intransversal section with respect to a first center of curvature andformed with a plurality of small arcuate sectional protuberancesextending in the longitudinal direction and distributed only in thetransversal direction, each of said small arcuate sectional protuberancebeing curved with respect to a second center of curvature, said firstcenter of curvature and each said second center of curvature beingselected to be positioned on the same side with respect to said metallicsheet, and a rigid synthetic resin layer covering both main surfaces ofsaid metallic sheet, said composite member being formed in a length,thelength of said metallic sheet being selected to be substantially thesame as the length of said length of the composite member, and saidplurality of small arcuate sectional protuberances being formed asprotuberances extending continuously throughout the length of saidmetallic sheet.
 2. A composite member in accordance with claim 1,whereinsaid metallic sheet are further formed with in-between arcuatesectional curved portions between the respective adjacent small arcuatesectional protuberances, each of said in-between arcuate sectionalcurved portions being curved with respect to a third center of curvatureselected to be located on the side opposite to that of said first centerof curvature with respect to said metallic sheet.
 3. A composite memberin accordance with any one of the preceding claims, whereinsaidplurality of small arcuate sectional protuberances are distributedequispaced throughout the width of said metallic sheet.
 4. A compositemember in accordance with claim 1, whereinsaid metallic sheet is curvedwith a first radius of curvature to be arcuate in transversal sectionwith respect to said first center of curvature, and the thickness ofsaid metallic sheet is selected to be smaller than 1/100 of said firstradius of curvature of said arcuate sectional curve with respect to saidfirst center of curvature.
 5. A composite member in accordance withclaim 1, which further comprisesan adhesive agent formed between saidmetallic sheet and said rigid synthetic resin layer for improvingadhesiveness therebetween.